Automatic telephone system



June 1 1926. 1,586,530

J. H. HOMRIGHOUS AUTOMATIC TELEPHONE SYSTEM Filed June-24, 1918 5 Sheets-Sheet 1 June 1 1926. 1,586,530

J. H. HOMRIGHOUS AUTOMATIC TELEPHONE SYSTEM Filed J 24 afar g m June 1 1926. 1,586,530

J. H. HOMRIGHOUS AUTOMATIC TELEPHONE SYSTEM Filed June 24, 1918 (5 Sheets-Sheet :5

Patented June 1 1926. l

ON I E T ES JOHN nJHoMiueHous, or OAK PARK; rnnmoisnssienon, BY MESNE ASSI NMENTS,

To AUTOMATIC 1 WARE.

ELECTRIG'IINQ; or CHICAGOQVILVLINOIS, A CORPORATION or DELA- UTOMA IC TELEPHONE SYSTEM.

' Application filed June24, 1918. Serial No. 241,516.

My invention relates to improvements in automatic telephone systems and more particularly to an improved method of controlhngnon-numerrcal switches of'the type em ployed in completing connections between calling llnes and trunk lines.

call originates in-such group and it quite frequentlyhappens-that if two subscribers remove their receivers at the same instant, the individual switches of these subscribers who have thus removed their receivers will: operate simultaneously :to seize the same. trunk 11ne. 1*

=An object-of my invention is; therefore,

a secondsidle trunk line. w

A further object of niyinvention the provision, in a g-systern in which -nonnumerical switches are controlled by master switches of the reciprocating type, of means whereby the master. switches control the nonnulnerical switches in such a manner that group will have accessto another idle trunk.

line at the same time, with aview vto reducing the time intervalrequiredfor intercom neetingr calling'lines andtrunk lines; Further olnects of" my invention relate to certain improvementsin the various swi ches employed allot which will .be more readilyunderstood by reference to the accompany" ing drawings, in which Ii-haveillustrated my invention in connection with, an auto matic telephone system embodying auto matic switches'lof the well known type Fig. 1 indicates acalling substation A,

whose line conductors 12 and 13 have been switch D to .a trunk line terminating in a selector switch'E.

" F 2 indicates aca-lling substationi A in another group of lineswhoseline conductors 1132 and v.113 have been extendedithrough the 7 medium of the individualline switch C and secondary line switch D in thesaine group asfsecondary line wami), to a trunk line,

"terminating ina selectorswitchlEl I Ithas usually been customary in the commercial operation of switches ofthis typeto preselect only'one idle trunk line for agroup of lines before a.

ber 290 comes Fig. 3 is a diagrammatic view showing the manner infwhich the primary and secondary ldred in e r p having m nacoess'to a small number of trunk lines which leadJto secondary switches :Dyan'di DI These sec ondary switches are arranged in groups j, j, "etc.', like .the primary switches, each group having access .to a smallnumber of trunk lines leading to selector switches E and E.

'Thes'e first-selector switches are arranged in groups Z, Z. etc.;; usuallyt'enm agroup hav I ,ingac'cessto other selectoiyswitches or con to partially overcome, the difliculty explained above by providing means for piieselecting nector- -switches; The trunksfileading from any one primary board do. not lead to any onesecondary board, but are distributed over aplurality of: secondaryboards. Likewise the trunksleading' from anyone secondary Qboard do not lead to any one group of first selector switches, but are distributed over a plurality of groups of selector switches.

Fig. at represents a perspectivefview of certain mechanical parts of the improved switch The frameand other unnecessary parts are omitted for .clearness in illustra tion and description.-

D Figure 5 shows aside elevation of the con-.

trolling 11111290 and the locki 1gplate229 1 in a position just before the vertical fmeinv intocontact witl the locking plate v229'.

Referriiigto-Eig. 4;, 8G designates a shaft mounted Jon supporting structure (not shown) The shaft 86 hasia relatively long vertical member 86 mountedfon horizontal extending" arms frointhe axis thereof.

The vertical member 86Qis adapted tojen; gagea notch in the'sector shaped member of the plunger 67 soxthat the rotation of the shaft will move the plunger 67? together with siinilarplungers in ahorizontal plane. lhe upper end oi: shaft 86 isprovided with a sector j shaped controllingplate the wide end of locking pla-te is provided with notches adapted tobe engaged by the controlling arm 83 in a manner iereinafter described; The lower end ofthe shaft 86 isprovidedwith a controlling 111290 which extends horizontallyfrom'the axis votthe shaft SG'and-is providedwith a verticalprojectii:gineinber290 adapted to engage the locking plate 220 on the upperend of shaft 230, The vertical member 200 is provided with an insulated knob adapted to operate the springs mount ed upon the locking plate 22-0. The shaft 80 rotates in a counter-clockwise direction by the tension of spring 97 and in a clockwise direction controlled by the solenoid to be hereinafter more fully described.

The shaft 230 is similar to shaft 86 except that it is rotated in a clock-wise direction by the engagement of the vertical member 200 contacting the locking plate 229, all of which will be more fully hereinafter described.

The automatic substations A. and A may be of any suitable or approved type, such for example, as the substation shown'in the British patent to Martin, No. 1,410, of 1910. Referring to the substation A, it comprises theu-sual receiver 7, transmitter 6, switchhook 8,, ringer '10 and condenser 11. Being an automatic substatiointhere is also provided a pair of impulse springsa and controlled by an impulse wheel 9 through the medium of a linger hole dial (not shown). The primary line switches (land-G are of the general type of line switch shown in the British patent to R. V, James, No. 26,301, of 1906, being, however, of the particular type shown in United States Letters Patent No. 1,078,690, granted January '17, 1912, to Frank Newforth. Through the medium of the line switch C the line of substation A is given access to a plurality of trunk lines each terminating in .a secondary switch.

The line switch C and a plurality-of other line switches are controlled in their trunk selecting operations by means of a master switch F. Likewise, the line switch C and a plurality of other line switches are controlled in theirtrunk selecting operations by means of the master switch 'F The master switches F and F are of the general type of master switch disclosed in the above mentioned British patent to James No. 26,301, of 1906, being however, more nearly of the particular type disclosed in United States Letters Patent No. 1,185,510, granted May 30, 1916, to A. E.'=Keith; As is well known, the function of the master switch is to maintain the plungers of all the idle line switches which it controls in position before the terminals of idle-trunk lines.

The secondary line switches D and D are similar to the primary line switches C and C. Through the medium of these secondary switches the trunk lines from the primary switches are extended to Etrunk lines terminating "in selector switches such as E and E,

The line switches 13 and *Dtogether with a plurality of similar switches arecontrolled in their trunk selecting operations "by means of a'master switch I The-master switch I is similar to the master switches F ant F except that the mode of operation is somewhat diii'erent and the circuits modified to operate in a system embodying the prince pics of my invention. As is usually the case in switches of this type the plnngers of all idle line switches which the master switch controls are in a position before the terminals of an idle trunk line. But I provide means whereby certain of the line switche; are in a position before one idle trunk while the remaining line switches which the master switch controls are in a position before a second idle trunk line.

Two trunk lines to which the secondary line switches and l) have access are indicated in the drawings Figs. 1 and 2, extending to-the selector switches E and E, respectively, of which only the line'and :releaserelays are shown. The selectors E and E may be of the type shown in United States Letters Patent to Newforth No. 1,078,690.

lVhile I have shown throughout the drawings a plurality of batteries it is to be understood that there may be but one battery having its positive pole grounded.

Having given a general description of the apparatus involved in the system, I wiil now proceed to explain more in detail the operations of the same.

When the receiver at substation A is removed from the switch hook preparatory to making a call, the engagement of the switch hook springs'completes a bridge across the line conductors 12 and 13. this bridge across the lineestablishes an energizing circuit for the line relay 1% of the line switch C. Relay 14, upon energizing, closes a circuit for the pull-in winding 15 at springs 16 by way oftcommon conductor 50. The -pull-in winding, upon (energizing, operates both the plungerarm 20 and the cut-off armature 21, the former through the medium of its plunger (not shown) forcing the ban springs 22 to 25,inclusive, into engagement, respectively, with contacts 26 to inclusive, and the latter disconnecting the line relay and ground from the line conduc tors 12 and 13, respectively.

It is assumed that immediately prior to the removal of the receiver at substation A the plunger of theline switch C and all the other plungers of'the idle line switches in the group were standing in a position before the terminals of the particular trunk line shownin the drawingsand which extends to the secondary switch D. vThis being the case, the master switch wiper 3% would at that time have'been in engagement with contact The locking arm 36 would have been'resting in notch 37 of the locking plate 38. With the master switch in this position as a result of "the engagement of spring 24: with contact a circuit for the starting relay 39 is closed by way of the master switch The closure of Y inasterswitch in the manner described until wiper 3 4 Upon energizing, the starting relay completes a circuit which includes the low resistance winding of the supervisory relay l0 and thewinding of relay 42 in series.

The locking relay 4-2, upon attracting its armature completes a circuit Wl11C-l1 includes the high resistance'winding of relay, 40 and the winding of relay 4 1 inparallel, and at the same time disengages the locking arm .361 from, the notch,37, thereby allowingthe plungershar't 43 to rotate in a counter-clockwise direction under springtension to the position shown in the drawlng. The relay -l1,uponenerg1z1ng, disconnects battery from the pull-in windings of all the line switches switch during that time. It isunderstood that by the rotation ofthe shaft 43 in the manner described the plungers i all idle, line switches are moved into position betore the terminals of the ninth trunk line-pro busy; Subsequent calls will now operate the I at such time when the plungers of all the widlelineswitch es are before the terminals of the first trunk line, in which case a line switch in seizing the "first trunk will coin-f plete a circuit for the starting relay 39 m the usual manner as .describedlabove, but

this relay uponenergizing at this time conipletes a circuit forthe relay 4% at springs 45 (pressed into engagement by arm @6) in parallel with the relay l2. The relay e4,

upon energizing, completes a holding circuit for the lookingrelay 42 to maintainjit energizedafter the wiper 34: ,hasmoved'ofi" of the grounded contaotfassociated with the 1 first trunk, and also 'colnpletes'a circuit for the solenoid 47.

nals oi the tenth trunk line, whereupon the plungersfiare before the terminals of the tenth trunk in which case the detent isdisengaged by the arm 49. I p h v As a further result of the engagement of sp i e with 3 311 Energizing Position before the terminals o'taiu'itue trunk, while, theplungers engaged by the cuit is coinpleted for the pull ii -winding of the secondary line switch D, as follows: springs 6911116170, slow actlng relay, 56, common conductor 68, springs 57, wind-y ings 62' and 63 of relay 58, springs 59 and low resistance winding of supervisory relay 66,. Relay 56 operates at this tnnefto close The solenoid now draws in its plunger, thereby rotating the plunger shafts?) inia clock-wise direction until the wiper 34 and all the plungers of the idle line switches reach a position before the termi a holding circuit for the 11 winding- T 3 oit the lme si itch C to prevent it tronii releasing, Relay 58, upon energizing, shorts ts high resistance winding 62, thereby allowing set-t jcient current to flow through the; pull-in w1nd1ng55 to operate 'the plunger ar'in'fii.

By'the engagementof spring 71 with spring 69 a holding circuit is completed iorfthc windingsjfio andr'EZ of. the secondary line sw tch n series over: the trunk conductor The circuit of relay 56 opened atsprings 69 and 70, but being slowto release its armature, it maintains the temporary medium of its plunger (not shown) iorces the {bank springs o-l to 54 inclusive, into engagement with contacts 7& to 77, inclusive, whereupon a circuit is completed for the holding circuit over the release" trunk coin tluctor 31 fo'rwinding 73 of the line switch cuntilthe plunger arm 67 through the line relay 78f0f theselectorswitchl), over,

trunk conductor 30, contact 26, spring p line 12,? to and through substation A, line vide'd that such trunk line is' not already" conductor 123, spring 25, contact 2S), and trunk conductor 33 Relay 78, upon eire'r gizingclosesa icircuit for release relay 79. 'R-elay m, upon energizing, completesaholding c'ircuit for winding 73 of line switch C atisprings 80,1 also closes a circuit forthe chain relay232,in-parallel with the winding :73. flAccordingly, relay 232 energizes and completes at contacts 2&2 one point in the circuit of stop relay 65. However, the cir- 'cuit'of relay 65 includes similar contacts on nine other chainirelays one or each oithe not, therefore, pull up at this timeQf Of'these chain'relays,'only chain relays231, and

Q lOare shown; y. t Alsothe chain relays23l, 232, etc., upon energizing 'short, theresistance ons 271, 272, etc, at springs 251, 252-, etc. respectively,v.for a purpose to be hereinlater de scribed, i j a i It is assumed that all the plnngers ot the idle secondaryfi switches in engagement with the shaft were standing in a positionjbefore the terminals er; the particular trunk,

line shown in'the drawing before the operationot' thelineswitchD- This bein the case the mastersw tch wiper -81 would atthat tinie have been in engagement with contact 82 ,"the locking arrirflS would have been resting in notch 8-1 of locking; plate 85, and as it has heretofore been stated an objectot' the master switch I isto maintain the plungersiengagedfby the shatt Min a :tact226.m The locking-arm 227 ,inight well be resting in. notch 2:28 of the lockingfplate,

a not already busy.

2:29. The rotation of the locking .plate 85 together with the shaft 86 in a counter clock-wise direction does not cause the plunger shaft 230 to move. i

As a result of the engagement of spring with contact 76, ground potential is placed upon contact 82 and its corresponding contact in the bank which master switch wiper has access to, thereby making the trunk line associated with that contact busy. Accordingly, a circuit is completed for wind ing 8?" of starting relay 89 by way of wiper S1. Relay 89, upo renergizing, opens the circuit of relay 60 at springs 94 and 95, and closes a circuit at springs 95 and $6 "for slow acting relay 61 and locking relay 90 in parallel. lielay 90 upon attracting its armature completes a circuit for the high resistance windin of supervisoryrelay so, atso at the same time discngages the locking arm 83 from the notch as, thereby allowing the plunger shaft 86 to rotate in a counterclock-wise direction by the tension of the spring 97 to the position shown in the drawing. The relay (31, upon energizing, disconnects battery from the common relay 58 in order to prevent the operation of any other line switches inengagenient with the shaft during the time that the plunger shaft is rotating. By the rotation of the shaft 86' in the manner described above all the phmgers of the idle line switches in engagement with the shaft 86 are moved to a position before the terminals of the eighth trunk lineg provided that such trunk line 15 The operation of other line switches whose plunger s' are engaged by shaft 86 will operate the'ma'ster switch in the same manner as described above until the plungers engaged by the shaft are in a position before the terminals of the first trunk line, in which case a secondary switch in operating to seize the first trunk line will cause the master switch to rotate in a clock ise direction which will be more fully described hereinafter.

The foregoing operations have all taken place in response to the removal of the receiver at substation A. The calling subscriber may now proceed to operate his calling device in accordance with the digits of the desired number whereby the selector E and succeeding switches are actuated in the regular manner to con'iplete the required connection.

I will now explain how the subscriber at substation A by the removal of the receiver from the switch hook upon initiating a call will establish a connection with the first selector switch E through the medium of his individual line switch C and the secondary line switch D. As the operations of the primary switch C, secondary switch D together with the master switch F is thesame as that described in connection with the primary switch C, secondary switch D, and master switch F, respectively; also as similar reference characters hay' e been given to like parts it is not thought necessary to describe the opcrations'in detail. Sol will proceed at onceto describe the operation of the master switch I when the trunk line terminating in the it selector switch E is seized by the operation of the secondary switch D. lit haying been assumed that immediately prior to the operation ofsecondary switch 3.) all the plunger-s of the idle line switches in engagement with the shaft 230 were standing before the terminals of the trunk "no leading to the selector E. "T he operation ofthe plungerarm 167 through the nediun'i of its plunger (not shown)" forces the banlcsprings 151 to 15a, 'iiic1usive,'into ene'ag ement with contacts 17 l o 177, inclusirel The engagen'ient of spring 15 3with contact 176 places ground potential upon the contact 226 and its corresponding contact'in the bank to which the wiper '81 liasa'ccess, thereby nzalrinjgj the trunk line a ociated villi thatcontact busy; Accordingly, circuit is ,con'ipleted for the winding 266 of startii relay 268 by ay of wiper Relay 2th). upon enci mn'g, closes a ciic uitfor relay and relay 2'50 in' parallel at springs 28:2 and 2C3: a d also closes a holding circuit for wind ing 26? of the'starting relay. lay 269', upon energizing, disconnects battery from the common relay 158 thereby preventing the operation of ai iyfot'hei' idle 'line switch in engagement with the shaft 230 during the time that 230' ismoying. Relay 210, upon energizing, closes a circuit tl'irough high resistance winding of supervisory relay 66, and at the same time disconnects tlielocking arm 227 from the notch thereby allowi the plungershaf t 230 to rotate in a counter-cloclr-wise direction by the tension of spring 293 until the locking plate 229 comes into cont-act with arm 290 which is secured to the plunger shaft" 86 in sucha manner that all the plunger's of the idle line switches in engagement with shaft 230 are moved in a position before the 'terminals of the same trunklines as the'plungers engaged by the shaft 86. The bushing carried on the vertical member 290 of thearm 290 is so adjusted as to operate the spri 9's mounted on the locking plate Rei idleytrunk line, whilethe plungers engaged,

by the shaft 230iw-ill bestanding before the terminals of the eighth trunk. Subsequent calls will now operate the master switch I in the manner described untilthe plungers engaged by the shaft 86 are in a position be- I tore the iirst trunln Supposing the plunge ers engaged by th shaft 86are standing beiore'the terminals of the first trunk line,

and a secondary switch is operated to seize that line thenia circuitis closed for winding 8: of'start ng relay 89in the usual manner.

Relay89, uponenergi'zi'ng, completes a cirouit for relay 91 through spring 93 closed by arm 98,.in; parallel with the relays and 61.

sition where the plungers are before the terminals of the tenth trunk. However, just before the vertical member 290 comes into engagementwithlocking plate 229, springs 288 are closed which completes a circuit for winding'267 of starting relay 268. Relay 268, upon energizing, completes a circuit for the relays 269 and 270. Relay269, upon energizing, disconnects battery from the common relay 163. Relay 270, upon ener gizing, disconnects the locking arm 227 from its position in a notch in the locking plate 229, whereby the shaft 230is rotated in a v clockwise direction by the solenoid 265 through the medium of arm 290 and locking plate 229. Although the circuit of relay 91 A is at once broken as soon as the arm 98 moves, its springs are held in an operated position by the-Edetent until the idle plungers are standing before-the terminals of the tenth trunk in which case the detent disengaged by the arm 99.1 And as a re- :sultfof the springs of relay 91 separating,"

the circuit for winding267 of starting relay S368 is opened; therefore,;tl1e idle plungers engaged-by the shaft 230will remain before the terminals of thetenth trunk unless that trunk is busy; By the operation of springs 286 on the locklng platev 229a holding c1rcuit was closed forwinding 88 of starting relay 89. The r,elay' 89 accordingly remains operated and causes the'shaft 86 to be actuatedthrough the medium of relay 90 in the same manner as described above to a position where the idle plungers are before the next idle trunk line...

Suppose the idleplungers engaged by the shaft186'are' before theterrninals of the first trunk line,"and the idle plungers engaged by the si nage are in a position before'thev terminals o'f the second trunk line in which case the operation of a secondary switch whose plunger is engaged by shaft 230 will causethe shaft to move to a position where all theidle plungers; are before the terminals of tlie"iirst trunk line e Operation of spring 289 by the arm 291 opens a point in tljiegcircuit of winding 88 of starting relay 5 89. Therefore, the shafts 86 and 280 remain invthat position untilany one of the secondary switches are operated toseize that trunk line, in which case the masterswitch I-will operate as previously described. I I

The operation'of the chainrelays 231, 232, 240, etc. as hereinbefore described shorts the resistance coils 271, 272,280, etc. respectively a 1n thecircuit of differential relay 295. I The relay 295 is so adjustedthat it willoperate its armature when only one of the resistance coils is connected in series with its right. hand windingand will release 'lllS armature I when twozor moreof the resistance coils are connected in series wit-h said winding, for

the purpose ofopening a point in the circult of w nding88 of starting rela 89, also a;point-in thevholding circuit of winding 261' of starting relay 26 8, so that all the idle plungers will be beforejthe terminals of the same-idle trunk line when-any nine of. the

trunk lines becomeybusy. Thus itwill be i seen that when only one trunk line the group is idle, there will be only one of' the relays ,I231,232,;240 eto. deenergized, and

the shaft 82 from moving its plungersaway therefore relay-295 will operate to prevent from the idle trunk line in an attempt to a move them opposite a second idle trunk-line when no otheridle trunk line is'tobe found; 1 hen the last trunk accessible to the line switches D, D, etc.,"becomes busy, the last open point in the; circuit of stop relay 65 is closed through springs 24:1, 242, 250, etc, whereupon relay GS-energizes and disconnects battery at springs 64 from the relays of the master switch I with the exception of the start relay 87,f from therelays 269 and 270, Fig. '2, and from the [solenoid 265 of the master switchI, This prevents any operation'at this-time of. the solenoid of the mats terswitch I andprevents alsothe energization of the relays named, At springs 26 1, stoprelay 65 placesground through springs of the relay 262 (which is normally ener gized through springs 95 and 94 of the start relay 89) on the common conductor 263 with p 'aresult to be pointed out below.

As a further result of the last trunk beis coming busy, circuits are closedifor the two startingrelays 268i and 89, whereupon these relays both energize. I springs 281 and 282 the circuit of the nor- Relay 268 opens at mally energized relaylGO, whereupon relayl 'falls back and grounds the associated" common conductor, thereby rendering busy an theidle line switches; controlled by the shaft 230. Start relay 7 89, upon energizing, opens at springs 95 and 94 the circuit for the the non-numerical switches in another to another one of 531d said trunk lines, and means for operating any one of said non-numerical switches in; another group to seize-another one of said trunk lines@ Y 10. In a telephone system, the combination of a non-numerical,switch having sets of passage contacts and a plurality of contact makers mounted to interconnect said passive contactswith amaster switch for controlling said non-numerical switch adapted to prei select a set of said contacts and to preselect a second, set of said contacts, and means for operating a plurality of said contact makers at the same instant to interconnectthe con tacts so'selected. y i I p 11. In a telephone system, a group of trunk lines, contacts serving as terminals of incoming] trunk lines and outgoing trunk' liI1S,,1116t111S for 'preselecting the contacts of an idle outgoing trunk line and. for pre-f selecting the contacts of a second idle outgoing trunk line in the same igroupya'nd means for interconnecting the contacts so selected at the same instant. p

12. In a telephone system, non-numerical trunking switches, a plunger for each switch, a first plunger controlling -sliatt, a second plunger controlling shaft, automatic inc-ans ttor rotating said first shaft to move a part of said plungers responsive to the rotation of said second shaft, and meansfor rotating said second shaftindependently of said first shaft to move a part of said plungers. 7 i

In a telephone system, trunk lines,

a *HOIl-lllllllGllCtll SWliJClI for connecting with said trunk lines, a plunger forsaid switch controlled by a' plungershatt, another non numerical switch having direct access to the same trunk lines, a plunger for said other switch controlled byanother plunger shaft, and a master switch for controlling said shafts ton'iaintain' the plungerv controlled by said first shaft in a position be fore the terminals of ,onetrunk line, and the plunger controlled'by saidsecond shaft in a position before the terminals ot'panother trunk line. M I i 14:. In a telephone system, trunk lines, non-nun'ierical switches forinterconnecting said trunk lines, a master switch tor'con trolling said non-numer cal switches adapt-i ed topreselect idle trunks, a chain relay energized upon the seizure of each trunk line,

another relay forcontrolling the operation of said master switch, said other relay operated when only one of said chain relays remains innor nal pos tioin I, 15. In a telephone system, trunk lines,

non-numerical switches .for interconnecting said trunklines, a m-asterswitch for con trollingsaidnon-numerical switches adapted to pi'eselect' idle trunks, a chain relay energized upon the seizure, of eaclrtrunlr line, another relay for controlling the operation of said master switclnsaid other relay operated when onlyflone ot' said chain relays remains in normal position and released when two Iofsaidlrclays are in normal position,

16, Inja telephone,system, trunk lines,

said trunk lines, a masterlswitch for con; trollingsaid non-numerical switches adapted to preselect idle trunks, chain relay en ergize-dupon the seizurevol' each trunk line, another 5 relay for "controlling the operation of sa d master swit'clnsa d other relay operated whentonly one of said chain relays rei mainsin normal; position and released when any two of said relays are in normal position, and althird relay forfurther 'controlling the operation of said master switch energizedwl'ien all of said chain relays, are energized.

17. In a telephone; system, trunlc liues, non-iiunierical switches for interconnecting "said trunk lines, a master switch for con 1 trolling said non-innnerical switches, adapted to. preselectidletrunks, a first relay for (controlling the operation of said master xswit'ch, ja normally closed c rcuit forsaid relay including a plurality of resistance coilsin series, another relay energized upon the seizure of a lillllll;11116,}Vl1e16lfi one of said resistance coils is shorted, said first reslay operated when only. one of said resist 'ance coils is included in said eircuit and releasedwhen any two of said resistance coils 211'8;1110l1l(l6(.l -111 sa d circuit;

non-numerical switches for" interconnecting 18. Ina telephone system, trunk lines, a non-nun'ierical switch tor interconnecting said trunk lines, a plunger fori said switch I controlled by" a'plunger shaft, another 1101 numerical switch, a plunger for said switch controlled by anotlierpl-unger shaftya mas ter switch for controlling said shafts wherev by the plungers' controlled by saidfirst shaft are in a. position he'forethe' terminals of a trunk line, and the plungers controlle'dlp; said second-shaft are in a position before the terminals of another/trunk line, and

means forop eratingany one of said plungers controlled by said second shaft while said firslfshattis moving. I r 19. In: astelephone system, trunk lines, a

non-numerieal switch for interconnecting saidtrunk lines, a plungertor said sw tch controlled by a plunger shaft, another nonnumerical switch, a plunger for said shaft controlled by another plunger shaft, a inaster switch for controlling said shafts where by the plungers controlled by said first shaft are in a position before the terminals of a trunk line, and the plung'ers controlled by said second shaft are in a position before the terminals of another trunk line, and means for operating any one of said plungcrs controlled by said first shaft while said second shaft is moving.

20. In a telephone system, trunk lines, a non-numerical switch for interconnecting said trunk lines, a plunger for said switch controlled by a plunger shaft, another nonnuinerical switch, a plunger for said switch controlled by another plunger shaft, a inastor switch for controlling said shafts whereby the plungers controlled by said first'shaft are in a position before the terminals of a trunk line, and the plungers controlled by said second shaft are in a position before the terminals of another trunk line, means for operating any one of said plungers controlled by said second shaft while said first shaft is moving, and means to prevent the operation of any of said plunger-s controlled by said first shaft while the same is moving.

21. In a telephone system, trunk lines, automatic switches for connecting with said trunk lines, means for positioning a group of automatic switches in alinement with an idle trunk and means for positioning a second group of automatic switches in alinement with a second idle trunk of the same group of trunks, means for operating an automatic switch in said second group to connect said second trunk line before said first idle trunk is connected with, and for actuating said second group positioning means.

22. In a telephone system, a group of trunk lines, automatic switches having access to and forconnecting with all the trunk lines of said group, preselecting means maintaining two trunk lines in the said group selectable at the same time, and means for operating two of said switches simultaneously to seize the two preselected trunks.

In a telephone system, trunk lines, automatic switches for connecting with said trunk lines, a master switch which operates to preselec't two idle trunk lines for said antomatic "switches, and means for preventing operationof the master switch to prcselect idle trunks when all of said trunk lines are busy.

.24. In a telephone system, trunk lines, automatic switches divided into groups for connecting with said trunk lines, a master switch for controlling said automatic switches which operates to preselec't two idle trunk lines, one for each group when two or more trunk lines are idle and which operates to preselect the same idle trunk line for both groups when all the remaining trunk lines are busy.

2-5. In a secondary trunking system comprising se'condary line switches and trunk lines accessible thereto, a control circuit, resistances equal in number to the number of said trunk lines included in said circuit in series, a relay individual to each trunk line for short circuiting the associated resistancc, and a marginal relay included in said circuit and adjusted to operate when all but one of said resistances are short circuited.

26; In a secondary trunking system comprising secondary line switches and trunk lines accessible thereto, a control circuit, resistances equal in number to the number of said trunk lines included in said circuit in series, a relay individual to each trunk line for short circuiting the associated resistance, and a marginal relay included in said circuit, said marginal relay being adjusted to operate when all but one of said resistances are short-circuited, and to fall back when two or more of said resistances are not short circuited. y

27. In a telephone system, a master switch comprising two mechanically cooperating but independently operable preselecting devices, trunk lines, a line switch having ac cess to said trunk lines and controlled by one of said devices, a second line switch also having access to said trunk lines butcontrolled by the other of said devices, means for operating said devices to preselect trunk lines for their respective switches, and means for preventing said devices from maintaining the same trunk line preselected.

In a telephone system, a master switch comprising two cooperating but independently operable preselecting devices, trunk lines, a line switch having access to said trunk lines and controlled by one of said devices, a second line switch also having access to said trunk lines but controlled by the other of said devices, means for operating said devices to preselect trunk lines for their respective switches, and means effective in case one of said devices preselects a trunk line that is already preselected by the other of said devices for re-operating said other deviceto preselect another trunk line. a 29. In a telephone system, two automatic switches, trunk lines each accessible to both switch-es, preselecting means for the first switch for bringing it, while still idle, into operative relation to an idle one of said trunk lines, similar means for the second switch, and means for preventing both switches from remaining in operative relation to the same idle trunk line.

30.111 a telephone system, a group of automatic switches, pre'selecting means common to such switches-a secondgroup of preselecting means being efi'ective to bring the idle'ones of its. own switches into opera tive relation to an idle trunk, and means for preventing the idle switches of both groups from remaining inoperative relate tion to the same idle trunk. I I 31. In a telephone system, two automatic switches, trunk lines each accessible to both switches, preselecting means for the first switch for bringing it, while still idle, into operative relation to an idle one of said trunk lines, siinilar means for the second switch, means for preventing both switches from remaining in operative relation to the saine'idle ti'unk line, and means for rendering the last named means inoperative in case a only one trunk remains idle.

In a telephone system, a group of au-i toinatlc' Switches, preselecting iiieansconuin case only one trunk remains idle.

'nion tov such switches, a 'seco nd group of automatic switch-es, preselecting means-coin mon to the second group, trunk lines each accessible to all of saidswitches, each of said automatic switches, preselecting means common to the second group, trunk lines each accessible to all ,ofsaidswitcheseach of said preselecting meanspbeing effective to bringt-heidle'ones of its own switches 1nto operative relation to an lCllQ trunk, means for preveiiting the idle switches of both groups from remaining in operative relation to the same idle trunk, and 'ineai s for rendering the last named means inoperative will automatically 33, In a switch which contact upon which to rest consequent to the Contact upon which it s then restmgbecoming busy, automatically applied means for rotateits test wiper seeking an idle bank ii'icapacitatingthe switch from rotating its said wiper when all other contacts normally accessible thereto are busy.

Signed by meat Chicago,

Cook County,

Illinois, this19t-h day of June, 1918.

I JOHN H. HOMRIGHOUS. 

